The miniaturization of electronic products is one of the primary tenets of technologic advance. Competitive advantage and the success of a product line largely hinges on the ability of a company to successfully provide products that are both increasingly functional and increasingly portable. As technology advances, it becomes increasingly possible to miniaturize electronic circuitry below human scale, with the result being that the interface alone (e.g., screens, keypads, cursor control devices) come to define the size of portable products. Therefore, the ergonomic quality and size of input devices (such as keypads) continue to have a growing significance to product acceptance and success.
One type of keypad or keyboard that provides a particularly space-efficient input means are Independent And Combination Key (IACK) keypads. IACK keypads have both independent and combination key regions, typically arranged in alternating rows and columns. An independent key, or independent key region, is an element of a keypad that, when pressed independent of adjacent keys, produces an associated output. By contrast, a combination key, or combination key region, is a keypad element with adjacent independent keys (such as at diagonally-oriented corners of the combination key region) that, when pressed in combination, produce an output associated with the combination key region. Typically, both independent and combination key regions will display graphics associated with their outputs.
IACK keypads represent an advance in keypad miniaturization, as they are readily configured to have an on-center distance between adjacent independent key regions about equal to one half the width of a typical adult human finger, or only about one-third of an inch.
One challenge of implementing such keypads is interpreting whether the user intends a combination or individual key output, especially in implementations with a desirably strong and definite tactile feedback, such as with polyester or metal snap dome keys. The discrete nature of such tactile feedback means may cause problems sensing combination key input when the finger is held at an angle during key actuation, as only one switch, or two adjacent and non-diagonally oriented switches, may be actuated when the underside of the keypad membrane “bottoms out” against the underlying printed circuit board (PCB), before activating a subset of independent keys necessary to identify the intended combination key. The result is that instead of registering the desired combination output, the system registers either an erroneous output of an independent key character, or nothing at all, in the case of two adjacent non-diagonally oriented keys.
Even when the finger is held correctly, some IACK keypads with strongly defined tactile feedback will, while providing an intended combination key output, produce a plurality of tactile or even audible “clicks” as the tactile elements actuate at slightly different times. Such multiple tactile or audible feedback is disconcerting, as it is inconsistent with the user's intent of indicating a single input. The result can be an unsatisfying tactile feedback experience.
Some successful IACK keypads employ rubber domes or other less defined tactile feedback means to “hide” the plurality of switch activations that occur during a combination key input. However, well-defined tactile feedback is highly desirable feature in many products, especially at the high-end of product lines. It is therefore highly desirable to provide a single, well-defined tactile feedback “click” for each IACK keypad input, whether the input is associated with a single independent key or a combination of adjacent keys.
Solutions to these and other keypad performance issues, both for IACK keypads and conventional keypads, are desired.
Some further background information regarding IACK keypad constructions can be found in my pending U.S. patent application Ser. No. 09/862,948 filed May 22, 2001, the entire contents of which are incorporated herein by reference as if fully set forth.